LU-1187 mdt: unlink remote directory

Send unlink req to the slave MDT, so both open/close
and unlink will send request to the slave MDT, where
the remote object resides. Then it would be able to
check orphan (unlink open file) locally.

Add lock_object api for enqueue remote object.

Change-Id: I7483b0f023e4e3de6597da58d3d9f3e96c0d53b7
Signed-off-by: Wang Di <di.wang@intel.com>
Reviewed-on: http://review.whamcloud.com/4339
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
LU-1187 mdt: add sanity check for rename and link

Add sanity check for rename/link, so remote rename/link
will return EXDEV.

Signed-off-by: wang di <di.wang@whamcloud.com>
Change-Id: I841c8ffaa74b162fcca5cd1661c383215350cccc
Reviewed-on: http://review.whamcloud.com/4348
Tested-by: Hudson
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>